Get the number of the Monday-starting week in the year and the day of the week.
The first Monday is the first day of week 1, any earlier days in the year are week 0 (as "%W" in Data.Time.Format.formatTime).
Monday is 1, Sunday is 7 (as "%u" in Data.Time.Format.formatTime).

Get the number of the Sunday-starting week in the year and the day of the week.
The first Sunday is the first day of week 1, any earlier days in the year are week 0 (as "%U" in Data.Time.Format.formatTime).
Sunday is 0, Saturday is 6 (as "%w" in Data.Time.Format.formatTime).

The inverse of mondayStartWeek. Get a Day given the year,
the number of the Monday-starting week, and the day of the week.
The first Monday is the first day of week 1, any earlier days in the year
are week 0 (as "%W" in Data.Time.Format.formatTime).

The inverse of sundayStartWeek. Get a Day given the year and
the number of the day of a Sunday-starting week.
The first Sunday is the first day of week 1, any earlier days in the
year are week 0 (as "%U" in Data.Time.Format.formatTime).